qt5declarative: fix examples compile without OpenGL support

qt5declarative: fix examples compile without OpenGL support

Fixes [1]:

   main.cpp:(.text._ZN11QQmlPrivate10createIntoI6FbItemEEvPv[_ZN11QQmlPrivate10createIntoI6FbItemEEvPv]+0x18): undefined reference to `QQuickFramebufferObject::QQuickFramebufferObject(QQuickItem*)'
   .obj/main.o: In function `QQmlPrivate::QQmlElement<FbItem>::~QQmlElement()':
   main.cpp:(.text._ZN11QQmlPrivate11QQmlElementI6FbItemED2Ev[_ZN11QQmlPrivate11QQmlElementI6FbItemED5Ev]+0x5c): undefined reference to `vtable for QQuickFramebufferObject'
   .obj/main.o: In function `QQmlPrivate::QQmlElement<FbItem>::~QQmlElement()':
   main.cpp:(.text._ZN11QQmlPrivate11QQmlElementI6FbItemED0Ev[_ZN11QQmlPrivate11QQmlElementI6FbItemED0Ev]+0x64): undefined reference to `vtable for QQuickFramebufferObject'
   .obj/main.o:(.data.rel.ro._ZTVN11QQmlPrivate11QQmlElementI6FbItemEE[_ZTVN11QQmlPrivate11QQmlElementI6FbItemEE]+0x48): undefined reference to `QQuickFramebufferObject::isTextureProvider() const'
   .obj/main.o:(.data.rel.ro._ZTVN11QQmlPrivate11QQmlElementI6FbItemEE[_ZTVN11QQmlPrivate11QQmlElementI6FbItemEE]+0x4c): undefined reference to `QQuickFramebufferObject::textureProvider() const'
   .obj/main.o:(.data.rel.ro._ZTVN11QQmlPrivate11QQmlElementI6FbItemEE[_ZTVN11QQmlPrivate11QQmlElementI6FbItemEE]+0xb4): undefined reference to `QQuickFramebufferObject::geometryChanged(QRectF const&, QRectF const&)'
   .obj/main.o:(.data.rel.ro._ZTVN11QQmlPrivate11QQmlElementI6FbItemEE[_ZTVN11QQmlPrivate11QQmlElementI6FbItemEE]+0xb8): undefined reference to `QQuickFramebufferObject::updatePaintNode(QSGNode*, QQuickItem::UpdatePaintNodeData*)'
   .obj/main.o:(.data.rel.ro._ZTVN11QQmlPrivate11QQmlElementI6FbItemEE[_ZTVN11QQmlPrivate11QQmlElementI6FbItemEE]+0xbc): undefined reference to `QQuickFramebufferObject::releaseResources()'
   .obj/moc_fbitem.o: In function `FbItem::qt_metacast(char const*)':
   moc_fbitem.cpp:(.text+0x70): undefined reference to `QQuickFramebufferObject::qt_metacast(char const*)'
   .obj/moc_fbitem.o: In function `FbItem::qt_metacall(QMetaObject::Call, int, void**)':
   moc_fbitem.cpp:(.text+0x80): undefined reference to `QQuickFramebufferObject::qt_metacall(QMetaObject::Call, int, void**)'
   .obj/moc_fbitem.o: In function `FbItem::~FbItem()':
   moc_fbitem.cpp:(.text._ZN6FbItemD2Ev[_ZN6FbItemD5Ev]+0x38): undefined reference to `vtable for QQuickFramebufferObject'
   .obj/moc_fbitem.o: In function `FbItem::~FbItem()':
   moc_fbitem.cpp:(.text._ZN6FbItemD0Ev[_ZN6FbItemD0Ev]+0x40): undefined reference to `vtable for QQuickFramebufferObject'
   .obj/moc_fbitem.o:(.data.rel.ro+0x8): undefined reference to `typeinfo for QQuickFramebufferObject'
   .obj/moc_fbitem.o:(.data.rel.ro+0x58): undefined reference to `QQuickFramebufferObject::isTextureProvider() const'
   .obj/moc_fbitem.o:(.data.rel.ro+0x5c): undefined reference to `QQuickFramebufferObject::textureProvider() const'
   .obj/moc_fbitem.o:(.data.rel.ro+0xc4): undefined reference to `QQuickFramebufferObject::geometryChanged(QRectF const&, QRectF const&)'
   .obj/moc_fbitem.o:(.data.rel.ro+0xc8): undefined reference to `QQuickFramebufferObject::updatePaintNode(QSGNode*, QQuickItem::UpdatePaintNodeData*)'
   .obj/moc_fbitem.o:(.data.rel.ro+0xcc): undefined reference to `QQuickFramebufferObject::releaseResources()'
   .obj/moc_fbitem.o:(.data.rel.ro+0xf0): undefined reference to `QQuickFramebufferObject::staticMetaObject'

[1] http://autobuild.buildroot.net/results/64a/64a198397736db12b73c1f693dbe1c47d73b53da

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>